1. Field of the Invention
The present invention relates to a wireless remote controller for a satellite radio receiver, and more particularly to a wireless remote controller which uses a time division duplexing system using a time division protocol, thereby being capable of overcoming a limitation on the directionality of remote control for a satellite radio while efficiently utilizing limited frequency resources to implement diverse additional information services. The present invention also relates to a satellite radio equipped with such a wireless remote controller.
2. Description of the Related Art
Most conventional AM/FM radios have a sound quality and reception sensitivity insufficient to meet the user's desire. In particular, in radios installed in motor vehicles, there are many difficulties in securing a desired reception sensitivity due to the mobility feature of those motor vehicles. In order to solve such a problem, satellite radios have been developed. Satellite radios can provide diverse digital services of high quality while maintaining a highly-sensitive reception state. However, such satellite radios have drawbacks when they are used in a running motor vehicle to provide music and other services of high quality. This is because the satellite radios have a complex configuration to provide many channels and diverse additional services, so that they cannot be conveniently manipulated by the user. For this reason, when a driver manipulates such a satellite radio installed in a motor vehicle while driving the motor vehicle, his attention to driving the motor vehicle may be reduced, so that an accident may occur. In order to allow the driver to conveniently manipulate the satellite radio without losing his attention to driving the motor vehicle, a remote controller for remotely controlling the satellite radio has been developed. This remote controller uses an infrared system mainly used in existing electronic products. However, the remote controller of such a type has a problem in that it must be used under the condition in which the driver pays attention to the directionality of the remote controller. Since the receiver unit of the satellite radio also has a limitation on its position due to the limited directionality of the remote controller, there may also be a problem in that where the satellite radio is installed at the central portion of the front panel in the passenger compartment of the motor vehicle, or at a position where the receiver unit cannot reliably receive a remote control signal from the remote controller, it is necessary to separate the receiver unit from the satellite radio, in order to install the receiver unit at a position where it can reliably receive the remote control signal from the remote controller. Furthermore, where the remote controller is configured to transmit digital data in an RF manner, its circuitry is complex. It is also necessary to secure error processibility and stability. For this reason, there is a problem of high costs. Meanwhile, wireless remote controller used in general satellite radios includes a combination of simple function keys. In other words, these wireless remote controllers have no hardware configuration capable of displaying information of diverse additional services, for example, a channel number, channel name, channel category, artist name, song title, subsidiary text, and diagnostic message.
Now, an example of conventional satellite radios will be described.
FIG. 1 is a schematic view illustrating a broadcasting system for a satellite radio broadcasting service, for example, a satellite radio broadcasting service provided by Sirius Satellite Radio Inc. Referring to FIG. 1, the satellite radio broadcasting system includes a radio studio 1, a studio-side repeater 3, a first remote uplink repeater 5, a second uplink repeater 7, a first radio satellite 9, a second radio satellite 11, a bi-directional communication satellite 11 such as a very small aperture terminal (VSAT) satellite, terrestrial repeaters 15, and base stations 17. VSATs are typically installed, for audio, facsimile, and data transmission, at out-of-the-way places, in the country, or farming and fishing villages where no terrestrial network is constructed.
The radio studio 1 produces a program to be broadcast, and transmits broadcast data of the produced program to the VSAT communication satellite 13 via the radio-side repeater 3 directly connected to the radio studio 1. Simultaneously, the radio studio 1 transmits the broadcast data to the first and second remote uplink repeaters 5 and 7 which, in turn, transmit the broadcast data to the first and second radio satellites 9 and 11, respectively. In response to the broadcast data, the first and second radio satellites 9 and 11 transmit satellite signals TDM1 and TDM2 to a mobile receiver, respectively. Meanwhile, the VSAT communication satellite 13 transmits an orthogonal frequency division multiplexing (OFDM) signal to the terrestrial repeaters 15, so as to cope with a reception difficulty caused by topographical or structural problems. The OFDM signal is transmitted to the mobile receivers via respective base stations 17 or respective terrestrial repeaters 15. OFDM uses a multi-carrier transmission system using several carrier signals, so as to divide a radio channel of a wide band into radio channels of a narrow band, thereby achieving transmission of a large amount of information and high-speed transmission. Thus, most areas receive two satellite signals TDM1 and TDM2, whereas the OFDM signal is used as a terrestrial wave for areas involving topographical or structural problems.
FIG. 2 is a block diagram illustrating the control circuit of a satellite radio system manufactured by Sirius Satellite Radio Inc. As shown in FIG. 2, the satellite radio system includes a tuner 20, a signal demodulating unit 30, a digital signal processing unit 40. The tuner 20 includes an RF processor 21 having a well-known configuration for dividing an input satellite signal into time division multiplexing (TDM) and OFDM components, and outputting the resultant signals. The signal demodulating unit 30 includes an analog/digital (A/D) converter 31 for performing a function of converting an analog signal into a digital signal, a demodulator 32 for demodulating digital data outputted from the A/D converter 31, a TDM selector 33 for selecting a signal having a highest signal-to-noise ratio (SNR) from TDM signals outputted from the demodulator 32, and an OFDM selector 34 for selecting a signal having a highest SNR from OFDM signals outputted from the demodulator 32. The signal demodulating unit 30 also includes a first memory 35 for providing comparative SNR data to the TDM selector 33 and OFDM selector 34, a signal mixer 36 for mixing signals outputted from the TDM selector 33 and OFDM selector 34, and a second memory 37 connected to the signal mixer 36. On the other hand, the digital signal processing unit 40 includes an oscillator 41 for outputting an oscillating signal of 16.384 MHz, a digital/analog (D/A) processor 42 for processing data received from an external controller 50 and a signal outputted from the signal mixer 36, thereby outputting analog signals, respectively, and third and fourth memories 43 and 44 connected to the D/A processor 42. An audio D/A converter 60 is coupled to the D/A processor 42, in order to output an audio signal and a stereo audio signal.
When a satellite signal having a bandwidth of 12.5 MHz while being centered on 2.32625 GHz is inputted to the satellite radio system manufactured by Sirius Satellite Radio Inc to have the above described configuration, the tuner 20 divides the inputted satellite signal into signals of different frequency bands, that is, TDM signals TDM1 and TDM2 and an OFDM signal. The TDM signals TDM1 and TDM2, and OFDM signal outputted from the tuner 20 are sent to the signal demodulating unit 30. In the signal demodulating unit 30, the signals are converted from an analog form into a digital form, and then subjected to a digital down-converting process. Subsequently, the resultant signals are demodulated, and then sent to the signal mixer 36. The signal mixer 36 selects a signal having a highest SNR from the TDM signals TDM1 and TDM2 and OFDM signal, and performs a forward error collection (FEC) process for the selected signal. The digital signal processing unit 40 digitally processes the resultant data obtained in accordance with the FEC process, and outputs the resultant digital audio signal in the form of an IbS (Philips Inter-IC Sound Interface) format. The audio signal has a basic sampling rate of 32 KHz, and a maximum sampling rate of 96 KHz. The interface of the digital signal processing unit 40 to the external controller 50 uses a synchronous serial interface (SSI) format. Generally, the external controller 50 may be implemented in the form of a wired or wireless remote controller (hereinafter, simply referred to as a “wireless remote controller”). Alternatively, the external controller 50 may be integral with the body of the satellite radio system.
However, the above mentioned conventional satellite radio requires a complex manipulation, as compared to traditional radios, because it has a configuration capable of providing music services of high quality and diverse additional services, even where it is installed in a motor vehicle. As mentioned above, when the driver manipulates an operating panel integral with the body of the radio or a wired remote controller during the driving of the motor vehicle, his attention to driving the motor vehicle may be reduced, so that an accident may occur. To this end, it is necessary to design a wireless remote controller capable of preventing the driver from losing his attention to driving the motor vehicle during the manipulation of the remote controller, in order to allow stable use of the satellite radio.
Infrared wireless remote controllers mainly used in existing electronic appliances should be used under the condition in which the user pays attention to the directionality of the remote controller. Also, the receiver unit adapted to receive a remote control signal from such an infrared wireless remote controller has a limitation on its position due to the limited directionality of the remote controller. For this reason, there may also be a problem in that where a satellite radio adapted to use such an infrared wireless remote controller is installed at the central portion of the front panel in the passenger compartment of a motor vehicle, or at a position where the receiver unit cannot reliably receive a remote control signal from the remote controller, it is necessary to separate the receiver unit from the satellite radio, in order to install the receiver unit at a position where it can reliably receive the remote control signal from the remote controller. Of course, the receiver unit is connected to the satellite radio by a cable. Furthermore, the infrared wireless remote controller implements a unidirectional communication, so that it can only transmit an operating command from the user, without having a signal reception function. Although bi-directional transmission of digital data can be achieved using two bands in a general RF system, there are various problems in this case. For example, the circuitry of the system is complex. It is also necessary to secure error processibility and stability. For this reason, there is a problem of high costs. A Bluetooth scheme is known as a standard wireless communication method. However, it is undesirable to apply the Bluetooth scheme to a wireless remote controller for use in satellite radios because Bluetooth modules are expensive. Also, the above mentioned infrared wireless remote controller has a drawback in that it cannot display information of diverse additional services, provided by the wireless satellite radio, to be identified by the user, for example, a channel number, channel name, channel category, artist name, song title, subsidiary text, and diagnostic message, because it uses a unidirectional communication system.